The present invention relates to an electrode catheter by means of which to map and if necessary perform an ablation internally of a cardiac cavity, in particular the right and left atria, the mitral valve and the ventricle.
Among the aims currently being pursued in medical and surgical technology, assisted not least by an increasingly widespread miniaturization and greater precision of the equipment available, there is a move toward the creation of a family of instruments which can be used, on the one hand, to monitor all such electrical activities of the cardiac muscle as will tend to widen the scope for the prevention of heart trouble, and on the other, simultaneously and where necessary, to perform a surgical operation. Whilst the measurement of electrical activity in the cardiac muscle is central to a full exploration of the cardiac cavities, the process of effecting the measurement is made difficult by the particular anatomy of the organ; the internal characteristics of the heart do not respond to a standard pattern, in effect, but vary from patient to patient.
As regards the treatment of heart diseases likely to generate situations of serious trouble, to the point of triggering fibrillation, the following options are available:
open heart surgery, performed to remove the zone affected by the trouble: an operation accompanied by risks and consequences well known to a person skilled in the art; PA1 installation of a defibrillator device, which will detect the trouble at the moment of onset and counteract the effect by producing a high voltage electrical discharge through a catheter implanted permanently in the patient: a solution involving high risk to the patient (insofar as the discharge can occur at any moment and without warning) and considerable cost: PA1 non-invasive sensing of the trouble zone by means of a probe, with immediate ablation of the affected muscle fibres: a more recently introduced technique which involves the least risk and disturbance for the patient.
At the time of filing the present application, the prior art embraces few instruments of diagnosis or surgery that can be utilized non-invasively in the manner referred to above, or at least to carry out an accurate measurement and a swift verification of the electric activity in the cardiac muscle. One such instrument consists in a unipolar or multipole electrode catheter insertable into the myocardium through a vein, of which the inserted end affords a sensor (or indeed a plurality of sensors in the case of a multipole type) connected electrically to external monitoring means, which can be maneuvered around internally of the cardiac zone in question. The catheter consists for practical purposes in a pair of parallel control wires united at one end by the terminal sensor and linked at the remaining or non-operative end to a control device functioning in the manner of a tiller, which when rotated one way or the other will impinge on a corresponding wire, causing the end of the catheter that carries the sensor or sensors to assume an arched profile; the arched portion can then be revolved through a plurality of positions in space by rotating the catheter about its own axis.
In this way, the surgeon can effectively "copy" the profile of the explored cardiac zone by sampling the electrical activity of the muscle discretely, with the aid of auxiliary computerized monitoring equipment which is programmed to make allowance for the dimensions of the electrode catheter, and in particular the distance of the operative portion from the point at which the catheter enters the cardiac cavity (referred to generally as the "zero" reference), and to calculate and map the copied profile by interpolation of the discontinuously monitored input data.
In the event that the exploration should reveal an irregular electrical activity in certain cardiac tissues, the selfsame device can be used by the surgeon to carry out an ablation in loco, that is, to burn away a small bundle of muscle fibres and thus eliminate the site of the irregular activity, by means of the terminal sensor utilized previously in the mapping operation; this would be effected with the aid, for example, of a radio frequency device.
The mapping device briefly outlined above betrays considerable drawbacks, however: the configuration of the catheter and the structuring of the wires and the relative control system combine to limit the radius of curvature available to the operative portion and thus allow no more than an approximate scanning and measurement of the cardiac cavities; also, the operations of calibrating and resetting the instruments are lengthy (even for very small dimensions) not least by reason of the fact that the reset (i.e. initial recognition of the "zero" reference) must be effected with a separate probe catheter which, once the position internally of the cardiac cavity has been located, will be removed to allow space for insertion of the mapping catheter, which in its turn must be positioned initially in relation to the zero reference in order to ensure that the zone is mapped correctly. Such a procedure obviously dictates a marked extension of the times required simply to perform the various steps, and this could be damaging to the patient ultimately, especially in cases where there may be the need to perform an ablation at sites registering irregular electrical activity.
In a further solution, disclosed in EP 499 491, the operative portion of the catheter incorporates a plurality of sensing poles or electrodes uniformly distributed along a probe capable of expanding axially in such a way as to allow of altering the distance between the single electrodes, from which corresponding signals are returned to an external controller; the multipole version of this device is somewhat complex, and in any event the catheter can not easily be adapted and matched to the different shapes of the cavities explored. As a result, there are difficulties in effecting the measurement part of the mapping operation, which remains lengthy and imprecise.
Accordingly, the object of the present invention is to overcome the drawbacks mentioned previously, by providing a cardiac mapping and ablation catheter of constructionally simple architecture, affording a wide range of configurations and thus adaptable to any cardiac cavity, while ensuring precision and completeness in every movement and in control over the configurations selected; such a catheter will allow a total and continuous scan of the zones of electrical activity and guarantee especially short operating times whether in monitoring or performing an ablation of cardiac tissue, and can be offered in a disposable format at relatively low cost.